Paging is a common technology in radio communication systems. It is applied in scenarios where a remote fixed station or a mobile terminal sends data to an access terminal (AT) in a radio communication system through the network. The network sends a paging message to access terminals according to the ID of each access terminal. The network entity controller in the network, which is responsible for sending the paging message, forwards the paging message to all the target access networks (ANs) within the paging area. These ANs then broadcast the paging message at a proper time.
The method for paging access terminals in the prior art includes the following steps: (1) The network entity that sends a paging message receives data from the network, and then sends the paging message to the current serving AN of the AT; (2) The current serving AN of the AT forwards the received paging message to each target AN; (3) Upon receipt of the paging message, each target AN calculates the time when the AT wakes to monitor the paging message according to some information carried in the paging message; and (4) At the calculated time, each target AN sends the paging message to the AT.
The key in the preceding method is to calculate the time when the AT wakes to monitor the paging message. To determine the time, there is a need to obtain the period that is adopted by the current AT and absolute time that is determined according to the time when the AT previously shifts from the connected state to the idle state.
The current paging message carries all the available periods of the AT. The message, however, does not carry the absolute time that is determined according to the time when the AT previously shifts from the connected state to the idle state. Therefore, in some special scenarios, the target AN fails to calculate the time when the AT wakes to monitor the paging message, thus missing paging the AT. The following describes two specific scenarios:
Before the AT disconnects and enters the idle state, the AT sends a Connection Close message to the current serving AN. The Connection Close message carries a future absolute time. The AT enters the idle state after the absolute time. The current serving AN sends the Connection Close message carrying the absolute time to the anchor AN of the AT or any other network entity that sends paging messages. In this scenario, if the target AN that wants to send a paging message to the idle AT does not receive a Connection Close message from the AT and the network entities do not carry the absolute time in the Connection Close message when sending the paging message to the target AN, the target AN cannot obtain the absolute time when the AT enters the idle state. Therefore, the target AN cannot use the method in the prior art to calculate the time when the AT wakes to monitor the paging message, and thus misses paging the AT.
When the AT is disconnected exceptionally, for example, the radio link is lost, the AT cannot send a Connection Close message to the current serving AN. Besides, the current serving AN cannot send the absolute time when the AT enters the idle state to the anchor AN or other network entities that send paging messages. Hence, in this scenario, if the target AN that wants to send a paging message to the idle AT is not the serving AN in the case of exceptional disconnection of the AT, the target AN that wants to send the paging message can neither obtain the absolute time when the AT enters the idle state and nor use the method in the prior art to calculate the time when the AT monitors the paging message.